The usual method of wheelchair movement is for the user to grip circular handrails fixedly mounted to the outside of the wheelchair's wheels. To do this, the user must continually grab, push and release the handrail. For many users, this action is very difficult or even physically impossible. Many devices in the art provide alternative wheelchair moving means which do not require the user to continually grip and release moving parts. Each of these devices in the prior art have disadvantages not shared by the device of this application. Some of the prior art devices restrict the free motion of the wheels increasing rolling resistance of the wheels and increasing the physical exertion required to move the wheelchair. Other devices in the prior art extend outside the wheels of the wheelchair increasing the width of the wheelchair and making the wheelchair more cumbersome to maneuver in tight spaces. Still other devices in the prior art require extensive mechanical modification of the wheelchair and hamper standard adjustments of the wheelchair increasing the cost and complexity of maintenance and repair of the wheelchair.
The following patents reflect the state of the art of which applicant is aware and are included herewith to discharge applicant's acknowledged duty to disclose relevant prior art. It is stipulated, however, that none of these references teach singly nor render obvious when considered in any conceivable combination the nexus of the instant invention as disclosed in greater detail hereinafter and as particularly claimed.
______________________________________ INVENTOR PATENT NO. ISSUE DATE ______________________________________ Krueger, T. F. 654,986 July 31, 1900 Williams, T. E. 838,228 December 11, 1906 Everest et al 2,643,898 June 30, 1953 Bulmer, D. L. 3,869,146 March 4, 1975 Lucken, W. O. 4,453,729 June 12, 1984 Korosue, A. 4,506,900 March 26, 1985 Tait, R. E. 4,735,431 April 5, 1988 ______________________________________
The patent to Bulmer teaches a device for moving a wheelchair without requiring the user to grip and release any moving parts. Bulmer is distinguishable from the device of this application in that the Bulmer device places the main lever arm outside the wheel on each side of the wheelchair. This increases the width of the wheelchair and increases the likelihood that the lever will catch on a passing object. Also, the lever of the Bulmer device is of a material flexible enough to allow the brake pad to engage the rim of the tire. This requires a material of sufficient flexibility.
The present invention utilizes a rigid lever with flexibility designed into the interface between the lever and its spindle sleeve. Furthermore, the device of this application has a spindle sleeve upon which the lever is mounted which isolates the lever from the wheel. This feature prevents the lever from interfering with the free rotation of the wheel and also allows the wheel to be easily removed or adjusted without removal of the wheelchair driving device.
The pawl construction of the instant invention is further distinguished over the pawl construction of the Bulmer device in that the curved toothed surface of the instant device more easily grips and releases the tires of the wheelchair. The construction of the pawl of the instant invention utilizes gravity to engage and release the pawl's curved toothed surface from the surface of the tire. This feature lessens the force necessary to engage and release the wheelchair driver while causing less wear to the tires. A corollary benefit to the curved tooth surface manifests itself when the chair travels in reverse.
The invention by Everest is of interest in that it has levers which the user can keep his or her hands on at all times. The device of this application is distinguishable from Everest in that the Everest patent requires substantial modification to the wheels of the wheelchair and also the Everest invention requires that the user learn to coordinate the power strokes of each lever together in alternating patterns while the device of this application allows a user to establish a motion pattern that is the most convenient, such as pushing together with both hands simultaneously. Furthermore, the Everest device lacks the simplicities of action associated with a pawl attached to a lever.
The patent to Tait provides a device which includes a lever which drives wheels of a wheelchair. The Tait device is substantially different from the device of this application in that it requires substantial modification of the standard wheelchair, requiring that gears and belt or chain drives be mounted on the wheelchair. The device of this application is easily attachable to a standard wheelchair and avoids interfering in any way with the existing operation of the wheelchair.
The other prior art patents listed above diverge more starkly from the present invention than those specifically distinguished. The device of this application provides a unique and useful method of modification of a wheelchair to provide users with limited physical abilities with a means for transporting themselves without assistance.